Selection in files with many objects
Here are a couple of things, you might want to try (actually, this is more of a comment than an answer, but I haven't earned privilege to make comments yet).


Selections in outliner (the right hand side panel) are much faster than in the 3d area. 
You can try hiding other objects with Shift+H (Alt+H to clear).
Alt+B will allow you to select a small portion (box select) to work in edit mode. You can switch back to the normal mode by pressing Alt+B again.